Tuesday, April 8, 2014

We finally cracked 60 degrees here at the end of the road, and the warm sunshine was irresistible. Yesterday, our spring butterflies turned out en masse for the first time this year.

Fifteen or twenty flitted about as only butterflies can, taking turns basking and puddling in our muddy driveway. But they only stayed for one sunny hour in the middle of the day. For now, the only butterflies we'll see during the warmest parts of these spring days are those species that overwinter as adults. Various other butterfly species overwinter as eggs, caterpillars or chrysalises, so we won't see them as fancy-flying adults until summer.

Why show up so early? Our driveway still harbors piles of crusty snow in the shady corners. The only wildflowers up so far are little buttercups, and I've never seen a butterfly feeding on them. As you may have noticed, not all butterflies feed on flower nectar. In fact, our spring butterflies rely mostly on tree sap and that insect super-food, animal dung. A nice pile of that is just the ticket after a long hibernation - the fresher the better.

Two adult Mourning Cloak butterflies basking in the sun

Yesterday's largest and shyest visitors wore the chocolate-brown wings of our state butterfly, the Mourning Cloak (Nymphalis antiopa). They're one of the most common butterfly species in the U.S., including all across Montana. Mourning Cloaks typically overwinter in tree crevices, and a sunny day can bring them out to fly in the middle of winter.

One of them (top left) looked a little worse for the wear, missing quite a few wing scales, which isn't unusual considering that he emerged from his chrysalis last July and is now an elderly eight months old. Shortly after emerging, the young guys rested through last summer's heat (estivation) before flying again last fall, feeding and storing energy for their torpor through the winter (hibernation). By last October they were hunkered down for the winter, just like us, waiting for this week to arrive. Now that it's finally spring-like again, these adults will fly, feed and mate, and females will lay their eggs between now and May.

Adult Compton Tortoiseshell butterfly

One medium-size butterfly also paid us a visit yesterday. The boreal Compton Tortoiseshell (Nymphalis vau-album) is a butterfly of southern Canada and northern U.S., including the northwestern corner of Montana.

He's also eight months old, but he remained active throughout last summer and fall before hibernating in November. Between now and June, the adults will mate and lay eggs that will hatch into a month-long caterpillar phase. Then each caterpillar literally melts inside a chrysalis and, like magic, fresh adults will emerge in July.

Adult Green Comma butterfly, also called the Green Anglewing

Flitting around these larger butterflies was a "flutter" of 10-15 smaller Green Commas (Polygonia faunus), which some folks know as Green Anglewings. Their wing scales use the same color pallet as the Tortoiseshell, but the outer wing margins are more deeply scalloped.

These guys are more easy-going than the other two species - a couple even landed on me - and they will eventually add nectar to their diet when the summer wildflowers finally arrive. But for now their menu is provided entirely by animals, in the form of dung and carrion.

The arrival of spring butterflies makes winter seem like maybe it wasn't so bad after all. Their reappearance also marks the start of a different season that you, like me, have no doubt been waiting for all winter. That's right, moth season is back!